A hybrid working machine which can effectively work by using motive power of an internal-combustion engine and motive power of electric machinery has been developed and used. The hybrid working machine may employ an operation mode of a so-called parallel type.
In the operation mode of the parallel type, a hydraulic pump and power machinery functioning as a generator and an electric motor are connected to an internal-combustion engine (an engine) in parallel as a power source to be commonly used. A hydraulic actuator is driven by the hydraulic pump, and simultaneously an electric power accumulator is charged by a function of the generator connected to the electric power accumulator. The power machinery may be operated as an electric motor by electric power from the electric power accumulator to assist the engine. The power machinery may be dual purpose machinery which integrally functions as both a motor generator and an electric motor. However, a motor generator and an electric motor may be separately used.
In the above hybrid working machine, the motive power for driving the hydraulic pump may be the output from the engine and the output from the motor generator assisting the engine. Therefore, the output from the engine and the output from the motor generator may be appropriately distributed in consideration of the states of the engine and the electric power accumulator for driving the motor generator.
It is proposed in a hybrid shovel that power for a pump is obtained, a distribution of electric motor power to be output in order to assist an engine with an electric motor is determined in response to the power for the pump, and a distribution of power is corrected to cancel a deviation between the target revolution speed of the engine and the actual revolution speed of the engine (for example, Patent Document 1).